Southeastern U.S. Daily Temperature Ranges Associated with the El Nino-Southern Oscillation

The daily temperature range (DTR; daily maximum temperature minus daily minimum temperature) at 290 southeastern U.S. stations is examined with respect to the warm and cold phases of the El Nino-Southern Oscillation (ENSO) for the period of 1948-2009. A comparison of El Nino and La Nina DTR distributions during 3-month seasons is conducted using various metrics. Histograms show each station's particular distribution. To compare directly the normalized distributions of El Nino and La Nina, a new metric (herein called conditional ratio) is produced and results are evaluated for significance at 95% confidence with a bootstrapping technique. Results show that during 3-month winter, spring, and autumn seasons DTRs above 29 degrees F (16.1 degrees C) are significantly more frequent during La Nina events and that DTRs below 15 degrees F (8.3 degrees C) are significantly more frequent during El Nino events. It is hypothesized that these results are associated spatially with cloud cover and storm tracks during each season and ENSO phase. Relationships between DTRs and ENSO-related relative humidity are examined. These results are pertinent to the cattle industry in the Southeast, allowing ranchers to plan for and mitigate threats posed by periods of low DTRs associated with the predicted phase of ENSO.